Renewable energy plays a critical role in the world-wide efforts to reduce fossil fuel use and curtail pollutions and carbon-dioxide emissions. Presently, wind and solar dominate the development and deployment of the renewable energy. Another source of the renewables is the kinetic energy in the moving waters on our planet. Although water typically moves slower than wind, water is more than 800 times heavier than air, and therefore has high energy density when it moves. Traditional methods of harvesting hydraulic energy often involve the construction of dams in/on rivers in order to increase flow velocity, which alters the natural flow of rivers and impose major disruptions to the environmental and ecological system in nature.
A major hydrokinetic energy source that is largely untapped is the moving water in the ocean. Great amounts of kinetic energy exists in the form of waves, tides, and ocean currents. A wave is the movement of water on the sea surface due to wind. The tide is the movement of water due to the gravity interactions of the earth, the moon and the sun. Ocean currents are the long distance movement of ocean water due to wind, temperature gradient, rotation of the earth, sanity gradients, etc. The present invention is a device used for the power extraction from ocean currents, tidal streams, and other fluid currents.
In the past there have been many different devices proposed in prior art to harvest the kinetic energy in water currents involving hydraulic turbines with rotating blades. Different types of turbines have been developed and are commercially available. Generally, submerged hydraulic turbines can either have a horizontal axis or a vertical axis. In many forms, the present invention uses the turbine with a horizontal axis. In some forms, the invention is a buoyant device that includes the hydraulic turbine, and a new method to tether the device in the middle of the moving water current, so that electricity can be continuously and effectively generated.
In several embodiments, the present invention has several distinctions and advantages, which may include: 1) in several embodiments, the present invention has a buoyant device tethered by mooring cables/tendons that are preferably in high tension; 2) in several embodiments, the present invention is totally submerged in the water and stays below the ship traffic; 3) in several embodiments, the present invention has the rotary turbine with its axis parallel to water flow direction and its blades sweeping in the plane normal to the water flow direction; 4) in several embodiments, the present invention uses single rotary turbine, but can easily be modified to house multiple-rotor turbines; 5) in several embodiments, the present invention uses three or more, parallel, non-coplanar, equal-length tethering cables/tendons; 6) in several embodiments, the present invention uses differential tensions in multiple, spaced cables to resist rotational moments; 7) in several embodiments, the present invention uses CG eccentricity method from self-weight and/or water weight in internal active ballast system to counter balance rotational moments; 8) in several embodiments, the present invention has yaw rotational capability by using two buoys, one rotating and the other non-rotating; and 9) in several embodiments, the present invention utilizes a weathervane to increase sensitivity to currents' direction change.
US 2009/0140524 to Keijha discloses a device with a single mooring line and single rotor turbine, but without discussion on the control of levelness and the roll and pitch motions. The operating position, as well as positions in different water flow conditions, may be very different from what is shown in the drawing. Keijha does not disclose the use of multiple, parallel, non-coplanar, equal-length tethering cable; use of differential tensions in multiple, spaced cables to resist rotational moments; or use of CG eccentricity method from self-weight and/or water weight in internal active ballast system to counter balance rotational moments.
U.S. Pat. No. 7,737,570 to Costin discloses a device with a single mooring line and single rotor turbine. Costin depends on large and spread buoyant bodies and internal water tanks to provide stability for the device. The device of Costin is not completely submerged and there is a need to pump water in and out of the device. Costin does not disclose total submergence in the water; use of multiple, parallel, non-coplanar, equal-length tethering cables; use of differential tensions in multiple, spaced cables to resist rotational moments; use of yaw rotational capability by using two buoys, one rotating and the other non-rotating; or utilization of an optional weathervane.
US 2010/0327583 to Hunt discloses a device tethered at one single point. Therefore, the levelness and stationary position of the device is maintained through the adjustment of the CO location and the hydrodynamic wings in response to the flow speed change. In US 2010/0326343, Hunt discloses a mooring method with minimum two cables connected to a single point on the device. The two-cable system as shown in Hunt cannot handle large flow direction change. Hunt does not disclose use of multiple, parallel, non-coplanar, equal-length tethering cables; use of differential tensions in multiple, spaced cables to resist rotational moments; use of yaw rotational capability by using two buoys, one rotating and the other non-rotating; and use of optional weathervane.
U.S. Pat. No. 7,291,936 to Robson is similar to Hunt—US2010/0327583, except it uses twin counter-rotating rotor, single mooring cable. The ballast system is used to introduce pitch and adjust angle of attack to control the depth of the device. Robson does not disclose use of a single rotary turbine, not dual rotors with opposite spin direction; use of multiple, parallel, equal-length tethering cables; use of differential tensions in multiple, spaced cables to resist rotational moments; use of a yaw rotational capability by using two buoys, one rotating and the other non-rotating; and an optional weathervane.
U.S. Pat. No. 8,766,466 to Dehlsen discloses two or more counter-rotating rotor assemblies. Dehlsen is a multi-rotor device with nonparallel mooring lines. Dehlsen also discloses that the vertical mooring line will not be engaged all the time. Dehlsen discloses that the wing depressor is used to provide a downward force in fast current. Dehlsen does not disclose use of a single rotary turbine; use of multiple, parallel, non-coplanar, equal-length tethering cables; use of differential tensions in multiple, spaced cables to resist rotational moments; use of a yaw rotational capability by using two buoys, one rotating and the other non-rotating; optional use of a weathervane.
U.S. Pat. No. 7,541,688 to Mackie discloses a semi-submerged device, with a minimum of one surface piercing strut always staying above the water surface. It is therefore a fundamentally different device from the present invention, which is completely submerged. The extensive use of flaps, hydrofoil wings, and lateral thrusters as disclosed in Mackie would interrupt the flow and introduce large drag, reduce the efficiency of the device. Mackie does not disclose the use of multiple, parallel, non-coplanar, equal-length tethering cables; use of differential tensions in multiple, spaced cables to resist rotational moments; use of a CG eccentricity method from self-weight and/or water weight in internal active ballast system to counter balance rotational moments; use of yaw rotational capability by using two buoys, one rotating and the other non-rotating; or use of an optional weathervane.
US 2010/02309711 to Mackie discloses the use of mooring cables with different angles to create the so-called “geofixed” buoy at the prescribed depth, essentially a virtual seabed above the natural seabed to provide an anchor place for the tethered turbine. The geofixed buoy and the turbine are two parts separated by long cable or tendon. The proposed mooring method of Mackie may be strong in restraining the linear movements of the buoy, but not as strong in restraining rotations. In several embodiments, the present invention has a rotational part and a non-rotational part closely attached through a shaft to form one device. The non-rotational part is not fixed in space. Rather, it moves as the speed and direction of the current changes, and is strong in resisting pitch and roll rotations. In several embodiments of the present invention the mooring cables maintain parallel, and the device translates without rotation during movement with the water flow. Mackie does not disclose use of multiple, parallel, non-coplanar, equal-length tethering cables; use of differential tensions in multiple, spaced cables to resist rotational moments; rotational capability by using two buoys, one rotating and the other non-rotating; or use of an optional weathervane.
U.S. Pat. No. 7,492,054 to Catlin discloses a floating device used at the water surface of river/tidal stream, deployed in plurality and interconnected by cables. Catlin is mainly floating, unlike several embodiments of the present invention. Catlin does not address the issues facing a submerged device with single turbine. Catlin does not disclose: use of multiple, parallel, non-coplanar, equal-length tethering cables; use of differential tensions in multiple, spaced cables to resist rotational moments; use of CG eccentricity method from self-weight and/or water weight in internal active ballast system to counter balance rotational moments; us of yaw rotational capability by using two buoys, one rotating and the other non-rotating; or optional use of a weathervane.
U.S. Pat. No. 8,272,831 to Johnston discloses a device with two counter-rotating rotors. It is totally submerged in the water and stay below the ship traffic. Johnston does not disclose: use of a single rotary turbine; uses of multiple, parallel, non-coplanar, equal-length tethering cables; use of differential tensions in multiple, spaced cables to resist rotational moments; use of CG eccentricity method from self-weight and/or water weight in internal active ballast system to counter balance rotational moments; yaw rotational capability by using two buoys, one rotating and the other non-rotating; or optional use of weathervane.
U.S. Pat. No. 4,306,157 to Wracsaricht discloses devices primarily using solid stiff supports, but two of its embodiments do use tethering cables, which are not parallel. The turbine is suspended from the floats above, and the only possible way to provide a stiff support from the floats is to use high tensions in the suspension cables. However, it is difficult to do so without causing slack in other cables. There is no discussion on pitch and roll motion control, an important issue for all floating devices. The device of Wracsaricht is unable to rotate to align with the changing flow direction. Key differences from the present invention include: In several embodiments, the present invention uses multiple, parallel, non-coplanar, equal-length tethering cables. In several embodiments, the present invention uses CG eccentricity method from self-weight and/or water weight in internal active ballast system to counter balance rotational moments. In several embodiments, the present invention uses yaw rotational capability by using two buoys, one rotating and the other non-rotating. In several embodiments, the present invention utilizes a weathervane.
U.S. Pat. No. 6,109,863 to Milliken discloses a submersible buoyant apparatus using dual rotors with vertical axes. The vanes (blades) of the rotors consist of many sub vanes that can open and close in designated directions, and thus to drive the rotor to rotate as the current passes through the device. The global stability of the device, not the focus of the invention, is questionable as the device is fully submerged and using only one mooring cable. Key differences from the present invention include: In several embodiments, the present invention uses the rotary turbine that has its axis parallel to water flow direction and its blades sweeping in the plane normal to the water flow direction. In several embodiments, the present invention uses single rotary turbine, not dual rotors with opposite spin direction. In several embodiments, the present invention uses multiple, parallel, non-coplanar, equal-length tethering cables. In several embodiments, the present invention uses differential tensions in multiple, spaced cables to resist rotational moments. In several embodiments, the present invention uses CG eccentricity method from self-weight and/or water weight an internal active ballast system to counter balance rotational moments. In several embodiments, the present invention uses yaw rotational capability by using two buoys, one rotating and the other non-rotating. In several embodiments, the present invention utilizes a weathervane.
U.S. Pat. No. 6,531,788 to Robson discloses the use of a twin counter-rotating rotor, single mooring cable. In Robson, a ballast system is used to introduce pitch and adjust angle of attack to control the depth of the device. The Robson device does not disclose: In several embodiments, the present invention uses single rotary turbine, not dual rotors with opposite spin direction. In several embodiments, the present invention uses multiple, parallel, non-coplanar, equal-length tethering cables. In several embodiments, the present invention uses differential tensions in multiple, spaced cables to resist rotational moments. In several embodiments, the present invention uses yaw rotational capability by using two buoys, one rotating and the other non-rotating. In several embodiments, the present invention utilizes a weathervane.
U.S. Pat. No. 6,856,036 to Belinsky discloses a semi-submersible platform with a Darrieus type turbines (vertical axis) suspended under the platform to harvest the kinetic energy of the flowing current. The device of Belinski lacks: In several embodiments, the present invention is totally submerged in the water and stays below the ship traffic. In several embodiments, the present invention the rotary turbine has its axis parallel to water flow direction and its blades sweeping in the plane normal to the water flow direction. In several embodiments, the present invention uses single rotary turbine, not dual rotors with opposite spin direction. In several embodiments, the present invention uses multiple, parallel, non-coplanar, equal-length tethering cables. In several embodiments, the present invention uses differential tensions in multiple, spaced cables to resist rotational moments. In several embodiments, the present invention uses yaw rotational capability by using two buoys, one rotating and the other non-rotating. In several embodiments, the present invention utilizes a weathervane.
U.S. Pat. No. 7,682,126 to Parker discloses an airplane-like device with dual rotors and single mooring cable. Parker depends on ballast water for pitch and roll control. The device of Parker lacks: In several embodiments, the present invention uses single rotary turbine, not dual rotors with opposite spin direction. In several embodiments, the present invention uses multiple, parallel, non-coplanar, equal-length tethering cables. In several embodiments, the present invention uses tensions in multiple, spaced cables to resist rotational moments. In several embodiments, the present invention uses yaw rotational capability by using two buoys, one rotating and the other non-rotating. In several embodiments, the present invention utilizes a weathervane.
U.S. Pat. No. 7,902,687 to Sauer has the main focus of the invention on the parts and assembly of the modular device and generator. It is a different kind of turbine with many foil shaped blades on a horizontal axis perpendicular to the water flow. The device of Sauer is not able to rotate with the change flow direction, although flow reversal is claimed to be allowed. Sauer lacks: In several embodiments, the present invention the rotary turbine has its axis parallel to water flow direction and its blades sweeping in the plane normal to the water flow direction. In several embodiments, the present invention uses single rotary turbine, not dual rotors with opposite spin direction. In several embodiments, the present invention uses multiple, parallel, non-coplanar, equal-length tethering cables. In several embodiments, the present invention uses differential tensions in multiple, spaced cables to resist rotational moments. In several embodiments, the present invention uses CG eccentricity method from self-weight and/or water weight in internal active ballast system to counter balance rotational moments. In several embodiments, the present invention uses yaw rotational capability by using two buoys, one rotating and the other non-rotating. In several embodiments, the present invention utilizes a weathervane.
U.S. Pat. No. 8,344,535 to Pitre discloses a platform-like device on water surface extracts power from the moving fluids on which it floats. Pitre uses helicoids flights (screw-like threads) blades on dual turbines. Pitre lacks the following from the present invention: In several embodiments, the present invention is totally submerged in the water and stays below the ship traffic. In several embodiments, the present invention uses single rotary turbine, not dual rotors with opposite spin direction. In several embodiments, the present invention uses multiple, parallel, non-coplanar, equal-length tethering cables. In several embodiments, the present invention uses differential tensions in multiple, spaced cables to resist rotational moments. In several embodiments, the present invention uses CG eccentricity method from self-weight and/or water weight in internal active ballast system to counter balance rotational moments. In several embodiments, the present invention uses yaw rotational capability by using two buoys, one rotating and the other non-rotating. In several embodiments, the present invention utilizes a weathervane.
US 2007/0231072 to Jennings discloses a submersible planar platform, consisting of a number of impellors, to be secured in the water column by mooring cables. Jennings uses taut cables from the floor and to the water surface. Jennings lacks the following: In several embodiments, the present invention is totally submerged in the water and stays below the ship traffic. In several embodiments, the present invention uses single rotary turbine, not dual rotors with opposite spin direction. In several embodiments, the present invention uses multiple, parallel, non-coplanar, equal-length tethering cables. In several embodiments, the present invention uses differential tensions in multiple, spaced cables to resist rotational moments. In several embodiments, the present invention uses CG eccentricity method from self-weight and/or water weight in internal active ballast system to counter balance rotational moments. In several embodiments, the present invention uses yaw rotational capability by using two buoys, one rotating and the other non-rotating. In several embodiments, the present invention utilizes a weathervane.
US 2008/0018115 to Orlov discloses a semi-submersible platform for power harvesting from the ocean current partially above the sea surface and with dual turbines. The device of Orlov has no rotational capability. Orlov lacks the following: In several embodiments, the present invention is totally submerged in the water and stay below the ship traffic. In several embodiments, the present invention uses single rotary turbine, not dual rotors with opposite spin direction. In several embodiments, the present invention uses multiple, parallel, non-coplanar, equal-length tethering cables. In several embodiments, the present invention uses differential tensions in multiple, spaced cables to resist rotational moments. In several embodiments, the present invention uses CG eccentricity method from self-weight and/or water weight in internal active ballast system to counter balance rotational moments. In several embodiments, the present invention uses yaw rotational capability by using two buoys, one rotating and the other non-rotating. In several embodiments, the present invention utilizes a weathervane.